Folding-competent and Folding-defective Forms of Ricin A Chain Have Different Fates after Retrotranslocation from the Endoplasmic Reticulum
Folding-competent and Folding-defective Forms of Ricin A Chain Have Different Fates after Retrotranslocation from the Endoplasmic Reticulum
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DOI：
10.1091/mbc.e09-08-0743
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发表时间：
2010-08-01
影响因子：
3.3
通讯作者：
Roberts, Lynne M.
中科院分区：
文献类型：
--
作者：
Li, Shuyu;Spooner, Robert A.;Roberts, Lynne M.
我们报告说，一种有毒的多肽保留的潜力重新折叠后，从内质网（ER）的胞质溶胶（蓖麻毒素A链; RTA）和错误折叠的版本，不能（称为RTA（三角洲）），遵循ER相关的降解（ERAD）途径，在酿酒酵母中的胞质溶胶中大幅发散。两种多肽在跨膜Hrd 1 p泛素连接酶复合物介导的步骤中移位，随后降解。典型的多泛素化不是这种相互作用的先决条件，因为无催化活性的Hrd 1 p E3泛素连接酶保留了逆向转运RTA的能力，缺乏一个或两个内源性赖氨酰残基的变体也需要Hrd 1 p复合物。在本机RTA的情况下，我们建立的位错也依赖于经典ERAD-L途径的其他组件，以及正在进行的ER-高尔基体运输。然而，进入胞质溶胶后，位错途径明显偏离。在这里，CDC 48复合物仅需要RTA（Delta），尽管蛋白酶体的19 S调节颗粒（RP）中的单个ATP酶（Rpt蛋白）的参与以及20 S催化室本身对于两种RTA变体非常不同。我们得出结论，胞质ERAD组件，特别是蛋白酶体RP，可以区分相同的基板之间的结构特征。
We report that a toxic polypeptide retaining the potential to refold upon dislocation from the endoplasmic reticulum (ER) to the cytosol (ricin A chain; RTA) and a misfolded version that cannot (termed RTA(Delta)), follow ER-associated degradation (ERAD) pathways in Saccharomyces cerevisiae that substantially diverge in the cytosol. Both polypeptides are dislocated in a step mediated by the transmembrane Hrd1p ubiquitin ligase complex and subsequently degraded. Canonical polyubiquitylation is not a prerequisite for this interaction because a catalytically inactive Hrd1p E3 ubiquitin ligase retains the ability to retrotranslocate RTA, and variants lacking one or both endogenous lysyl residues also require the Hrd1p complex. In the case of native RTA, we established that dislocation also depends on other components of the classical ERAD-L pathway as well as an ongoing ER-Golgi transport. However, the dislocation pathways deviate strikingly upon entry into the cytosol. Here, the CDC48 complex is required only for RTA(Delta), although the involvement of individual ATPases (Rpt proteins) in the 19S regulatory particle (RP) of the proteasome, and the 20S catalytic chamber itself, is very different for the two RTA variants. We conclude that cytosolic ERAD components, particularly the proteasome RP, can discriminate between structural features of the same substrate.